The namesake blue mists of the Great Smoky Mountains National Park long ago gave way to the white haze that tourists now peer through, a legacy of power plants whose emissions still smother the park.
Pollution pares long-range visibility to as little as a mile, sours trout streams and leaves 10 million visitors a year breathing mountain air that's likely to be dirtier than what they have back home.
Now the park, whose 850 square miles straddles the N.C.-Tennessee line, is in the midst of legal and political fights that could shape its future.
A federal judge in Asheville is hearing North Carolina's lawsuit to force the Tennessee Valley Authority to reduce emissions from its coal-fired power plants. More effective pollution controls, the state says, could save lives and improve the health of the park.
Environmental groups have filed suit to stop expansion of Duke Energy's Cliffside coal-fired power plant, 80 miles east of the park. The National Park Service says the 800-megawatt addition would worsen haze and add to the toxic mercury and tons of acidic chemicals that fall here each year.
The Bush administration, meanwhile, is expected to adopt a rule this year that critics – including federal scientists and U.S. Sen. Elizabeth Dole. R-N.C. – say could allow more pollution to be blown into national parks. Critics say the change would mask the problems by ignoring short-term pollution spikes.
As it is, the Great Smoky is not only the most-visited national park but the most acidic. Its high-elevation soils are so saturated with pollution falling from the air that experts say it will take decades to recover.
“They can't even begin to recover until you turn off the spigot. But we continue to put more acid into the system,” said Mark Wenzler, clean-air director for the National Parks Conservation Association.
The acid finds its way into headwater streams high in the Smokies, once ruled by a jeweled dart of a fish called the brook trout.
Its habitat trashed by long-ago loggers, its pools and riffles taken over by non-native competitors, the brookie has fought its way back toward recovery.
There's one nagging problem: keeping water pure enough for its comeback.
An overgrown trail on the park's 5,500-foot Noland Divide leads to an outdoor laboratory that for 16 years, drop by drop, has recorded the acids falling from the sky.
An assortment of concrete weirs, buckets and tubing, some of it guarded from marauding bears by an electric fence, sit among towering Fraser firs and two streams bubbling from the mountainside. Students from the University of Tennessee visit every two weeks to collect water samples and download readings.
Once acids soak into the soil, they can stay for decades. They leach out nutrients that trees need and release aluminum that's toxic to fish. Each time it rains enough can flow into streams to acidify them too.
Rainfall at Noland Divide averages a pH of about 4.2, more than 10 times as acidic as clean rain. The streams average about 5.5, the point at which trout are stressed and begin to have reproductive problems.
A rain shower can quickly wash a near-lethal jolt of acidity into the streams, possibly killing young fish and the insect larvae they feed on.
If rising trends continue, one study found, two-thirds of the park's streams could grow acidic enough to harm fish in less than 25 years. Tennessee has listed 10 streams on its side of the park as impaired by acidity, and those on the N.C. side fit the description.
“This is the invisible effect of air pollution that nobody sees and nobody thinks about,” said Steve Moore, a park fishery biologist.
Brook trout have lost up to three-quarters of their former range in the park because of introduced rainbow trout and turn-of-the-century logging. Now, after years of work to eradicate the rainbows, brookies are coming back. Two years ago, the park removed a fishing ban that dated to 1976.
“We can restore and continue to restore,” he said. “But if we don't get a handle on acid deposition it can all be for naught.”
Jim Renfro, the park's longtime air-quality specialist, sees improvement in the air since the late 1990s. Visibility on the haziest days has gotten better. Last year saw the lowest amount of sulfate and nitrate in rainfall since record-keeping began in 1980.
“In the last 10 years, no key measurement is getting worse,” he said. “That's huge.”
But reversing the damage of decades will take more decades, he said, even if power plants stop belching sulfur dioxide. The park's high peaks, heavy rainfall and tendency to trap stagnant air, combined with dozens of upwind power plants east of the Mississippi, all work against cleanup.
The park's air violates the federal ozone and fine-particle standards, prompting health warnings to hikers. Ozone levels are some of the highest in the East, with readings on the ridgetops up to twice those of Knoxville and Atlanta.
The park's verdant greenery is also at risk. Ozone may cut the growth of trees in the park by up to half and greatly reduce the number of flowers and seeds that wildflowers produce, scientists have learned.
More recent research in the park found that trees exposed to high ozone levels lose increased amounts of water through pores in their leaves, in turn sucking up more water from the soil around their roots. The effect is so pronounced that nearby streamflows may drop, causing problems for fish and compounding droughts that could become more frequent as the climate warms.
On the ground, an 80 percent reduction in acid deposits is needed to return the park to natural conditions, Renfro said.
“For the air pollution to come back out of the soils,” he said, “is going to take time. It may continue to get worse before it gets better.”